Plug connector thermally responsive overload circuit breaker



y 23, 1967 K. M. DELAFRANGE 3,321,596

PLUG CONNECTOR THERMALLY RESPONSIVE OVERLOAD CIRCUIT BREAKER Filed Dec.21, 1965 \i zg I; ag! Q m 1] o o o o O O O o o o o o x/vz avmk 8y wgmwUnited States Patent Ofifice 3,321,596 Patented May 23, 1967 3,321,596PLUG CONNECTOR THERMALLY RESPONSIVE OVERLOAD CIRCUIT BREAKER Kenneth M.Delafrange, 96 Washington Ave., Westwood, NJ. 07675 Filed Dec. 21, 1965,Ser. No. 515,405 Claims. (Cl. 2tl0116) This invention relates toimprovements in thermally responsive overload electrical circuitbreakers of the quick detachable plug-in type.

The invention has as its object provision of a simplified manual reseteconomical plug-in overload circuit breaker which may be installed andused permanently in substitution for fuses in new and old wiringsystems, fuse boxes, circuit connector panels and the like, thusavoiding dangers attending fuse replacements, and also avoiding thetroublesome necessity of keeping at hand a number of fuse replacementsfor restoration of service after a circiut fault correction.

Objectives of the invention are accomplished by a simple in line circuitbreaker structure economical to manufacture, an emobdiment of which ishereinafter described and illustrated in the accompanying drawingwherein I FIG. 1 is a side view in elevation of an embodiment of theinvention, the view being partly broken showing in cross section acircuit breaker latch and reset detail.

FIGURE 2 is a vertical median cross section on line 22 of FIG. 1 showingone of the counter part halves of the body structure of FIG. 1 and withthe circuit breaker assembled therein.

FIG; 3 is a horizontal cross section of an assembled p ug body taken online corresponding to line 33 of FIG. 2.

FIG. 4 is a median cross section view corresponding to that of FIG. 2but showing a modified circuit breaker arrangement.

FIG. 5 is an end FIGS. one to three.

Having reference to FIGS. 1-3 of the drawing there is shown a screwshell type thermally responsive circuit breaker 1 comprising aconventional screw shell contact for detachable association with a screwshell socket surrounding an insulator plug body of abutting halfportions 2 and 3, each portion being internally recessed and providedwith countersunk holes therethrough adapted to register with holes inthe counterpart portion and be fixed securely together by tubular rivets4. The inner recess 5 in plug portions provide air ventilation forbreaker units between inwardly directed ribs 6 and in the bottom recessportion provide expansion room and guide space for breaker elements.Ribs 6 centrally position the circuit breaker assembly and affordminimum frictional contact therewith.

Before jointure of plug portions, however, the circuit breaker assemblyis installed within and between the plug portions. This circuit breakermechanism includes a helical spring form high temperaturenickel-chrominurn alloy conductor 7 fixed at one end to a conductorcontact 8 seated in a receiving slot in the body portions andoverlapping the plug end to constitute the center contact of the plug.While the conductor contact 8 may take other forms not shown, thiselement serves as firm anchor for one end of the spring form conductor7. At its other or free end the helical conductor is fixed to andcarries a movable contact bar 9 extending laterally in a bottom recessportion into overlapping contact with fixed contact 12 of connection 10soldered at 11 to the lower edge portion of the screw shell contact.Thus in its normal state the circuit breaker is electric current planview of the circuit breaker of conductive through center contact 8,spring form conductor 7, contact bar 9, contact 12, conductor 10 and itssoldered connection with the screw shell contact.

Spring form conductor 7 is preferably of Nichrome wire predetermined asto gauge and extent to conduct electric current therethrough within apredetermined load consuming current value range without distortion ofthe conductor. The spring form conductor is lightly tensioned in itsinstallation to effect positive overlapping pressure of contact bar 9 onfixed contact 12. Such constitutes normalcy of the breaker arrangementthroughout normal predetermined safe current load range for which thebreaker is designed.

The helical spring form conductor has a high coefficient of exapnsion sothat on occurrence of overload current beyond that for which the breakeris designed the spring form conductor instantly overheats forcing linearexpansion thereof to separate contact bar 9 from fixed contact 12 tobreak the circuit. In the normal reaction after having broken thecircuit, the spring form conductor on cooling contracts to cause closureof the contacts and the circuit. However, this is preventedautomatically by a spring loaded latch and reset member 14 havingintermediate trunnion portions pivotedly mounted in mating recesses inthe plug half portions, a hook form inner end portion in contact withthe side of contact bar 9, a spring 15 forcing the latch into suchcontact and an outer finger tip operable lever portion normally housed,as to main body part, within a provided recess in the outer end of theplug body. The inner hook end of the latch and reset member at itscontact with contact bar 9 is beveled or rounded for minimum frictionalcontact engagement with the bar and is provided with a lateral flangeportion operable when the circuit breaker functions on overload tointerpose its insulating body between the fixed and movable contactspreventing arcing and reclosure of the contacts and the circuit.

The latch and reset member being fixed as to position functionsimmediately on expansion of the spring form conductor to commenceengagement behind the moving switch bar contributing to speed of contactseparation by the pressure of the latch swinging into lock out positionbehind the bar. Simultaneously in this operation of the breaker theopposite end finger tip lever portion of the latch and reset memberswings outwardly of its accommodating recess to resetting position.Sides of this lever end portion may be colored red or as desired toindicate to a user the breaker condition which is also shown of courseby the swung down position of the lever. To reset the breaker after acircuit fault has been corrected it is only necessary to push the latchand reset lever end back into its recess against the spring tensionthereon. This swings the latch out of its engagement behind the contactbar and its insulating and are prevention flange from between thecontacts which close with snap action under tension of the cooled springconductor.

FIG. 4 shows a modified structural arrangement wherein the breaker issubstantially as previously described except that contact bar 9 has onits rear side thereof a thin ferrous armature backing strip 17, and, inlieu of the latch member an insulation slide 18 normally has an endportion in engagement with the side of the contact bar 9 and its sideedge portions sl-id'ably mounted in guide recesses in the plug portions.An angular pivoted lever 19 has an inner end portion extending throughan aperture in the insulating slide to eifect its slidable operations.Intermediate the lever end engaged through the slide and the fulcrumportion of the lever pivoted in recesses in the plug halves there isprovided a ferrous armature 24 fixed to the lever and cooperative with a22 below the contact bar at the bottom of the recess. This magnet iscoextensive with the underlying armature strip 17 on the contact bar andhas a beveled end portion defining greater extent of the magnet at thebottom than at the top. With the insulator slide retracted to its normalposition by the lever the armature 24 is in close proximity with thepermanent magnet at lower edge portions of the armature and magnet sothat the armature is in the magnetic field to cause pivoting of thelever. End engagement of the insulator slide with the contact barprevents this action until the circuit breaker operates under overload.When overload operation happens the contact bar quickly moves out ofcontact with the insulator slide end, the lever then swinging underinfluence of the permanent magnet to project the insulator slide inposition between the fixed and movable contacts.

The other or outer end portion of the lever extends through a slot 23 ina manual reset button 21 headed at its inner end and extending throughapertures in the permanent magnet and the plug end portion outwardly ofthe plug for reset operation.

The air gap between the permanent magnet and armature strip 17 is suchthat the armature remains affected by the permanent magnet but in aportion of the magnetic field wherein the greater forces of thetensioned spring form conductor overrides the permanent magnet force.When the circuit breaker is subjected to abnormal overload current andoperates, the armature 17 moves closer to the ermanent magnet and intoincreasing power of its magnetic field. When the circuit breakeroperates under overload conditions, however, its circuit breakingoperation is enhanced by the magnetic pull. The circuit breaker ismanually reset in this structure merely by finger pushing the resetbutton inwardly which retracts the insulator slide and forces thecontact bar and its armature inwardly and away from the permanent magnetuntil overriding pull of the helical conductor is effective to close andhold closed the circuit contacts.

Having described the invention in connection with a preferred embodimentthereof, the words employed are those of description rather than oflimitation as changes in structure and types of contacts arecontemplated within the purview of the appended claims without departurefrom the true scope and spirit of the invention.

I claim:

1. In an electrical plug connector thermally responsive overload circuitbreaker, an insulating plug body having mounted thereon an externalscrew shell contact and permanent magnet internally recessed to receive,hold and position therein an overload circuit breaker assembly andprovide operational space therefor, a fixed contact extending into saidoperational space and connected with said screw shell, circuit conductormeans supported within the plug recess fixed at one end of the plug forcircuit continuity therethrough from a conventional electric screw shellsocket and provided at an inner free end with a contact member normallyengaged with said fixed contact, said circuit conductor means directlyincluding between the fixed end thereof and its. free end in circuitconnection with said fixed contact a helical spring form conductor ofnickel-chromium alloy composition and of predetermined size andconductive capacity, said helical spring form conductor normallymaintaining ciated contact in conductive engagement with said fixedcontact throughout a predetermined normal load current flow range butsubject to linear expansion to separate the contacts and break thecircuit continuity under heat generated in the helical conductorresultant from overload current flow above said range.

2. An overload circuit breaker as defined in claim 1 characterized byautomatic means operable on separation of the contacts to prevent arcingand reclosing of the contacts until said means is manually operated toallow the contacts to reset.

3. An overload circuit breaker as defined in claim 1 characterized byautomatic means comprising a pivoted spring loaded latch-leverpreventing reclosing of the contacts separated as result of overloaduntil the latch-lever is manually operated to release the latch to allowthe contacts to reset.

4. A plug connector overload circuit breaker as defined in claim 1characterized by a permanent magnet in the bottom recessed portion ofthe plug and an armature fixed to said helical free end contact memberwith an air gap between the magnet and armature which decreases in eventof linear expansion of the helical conductor.

5. A circuit breaker structure as characterized by the plug bodycomprising two counterpart half portions interiorly recessed toaccommodate and hold the circuit breaker and ing the half portionstogether.

No references cited.

BERNARD A. G'ILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner.

its free end asso-- defined in claim 1' parts positioned byfasten-

1. IN AN ELECTRICAL PLUG CONNECTOR THERMALLY RESPONSIVE OVERLOAD CIRCUITBREAKER, AN INSULATING PLUG BODY HAVING MOUNTED THEREON AN EXTERNALSCREW SHELL CONTACT AND INTERNALL RECESSED TO RECEIVE, HOLD AND POSITIONTHEREIN AN OVERLOAD CIRCUIT BREAKER ASSEMBLY AND PROVIDE OPERATIONALSPACE THEREFOR, A FIXED CONTACT EXTENDING INTO SAID OPERATIONAL SPACEAND CONNECTED WITH SAID SCREW SHELL, CIRCUIT CONDUCTOR MEANS SUPPORTEDWITHIN THE PLUG RECESS FIXED AT ONE END OF THE PLUG FOR CIRCUITCONTINUITY THERETHROUGH FROM A CONVENTIONAL ELECTRIC SCREW SHELL SOCKETAND PROVIDED AT AN INNER FREE END WITH A CONTACT MEMBER NORMALLY ENGAGEDWITH SAID FIXED CONTACT, SAID CIRCUIT CONDUCTOR MEANS DIRECTLY INCLUDINGBETWEEN THE FIXED END THEREOF AND ITS FREE END IN CIRCUIT CONNECTIONWITH SAID FIXED CONTACT A HELICAL SPRING FORM CONDUCTOR OFNICKEL-CHROMIUM ALLOY COMPOSITION AND OF PREDETERMINED SIZE ANDCONDUCTIVE CAPACITY, SAID HELICAL SPRING FORM CONDUCTOR NORMALLYMAINTAINING ITS FREE END ASSOCIATED CONTACT IN CONDUCTIVE ENGAGEMENTWITH SAID FIXED CONTACT THROUGHOUT A PREDETERMINED NORMAL LOAD CURRENTFLOW RANGE BUT SUBJECT TO LINEAR EXPANSION TO SEPARATE THE CONTACTS ANDBREAK THE CIRCUIT CONTINUITY UNDER HEAT GENERATED IN THE HELICALCONDUCTOR RESULTANT FROM OVERLOAD CURRENT FLOW ABOVE SAID RANGE.